1. Field of the Invention
The present invention relates to electric motors, and particularly motors of a type that are used as the main drive motor for a domestic laundry.
2. Description of the Related Art
EP 1548171 describes a drive system for washing machines. The drive system comprises a motor with a large diameter shallow stator and a rotor with magnets external to the stator. The stator is supported on the end of a washing tub as shown in FIG. 2 of that application. The stator has an aperture for a drive shaft to pass through. As shown in FIGS. 2 and 16 of EP patent application 1548171, a rotor, which is to be fixed to the drive shaft for driving the rotating drum of a washing machine, has a ring of permanent magnet material supported on the inside of a steel backing ring. A frame extends between the hub of the rotor (through which the shaft can extend) and the steel backing ring. The backing ring and frame may be formed together. The permanent magnet material is made of a set of curved permanent magnet elements. The permanent magnet material is magnetised after physical construction of the rotor. A typical rotor has more than 30 poles magnetised into the ring of magnetic material. The polarity of the poles alternates proceeding around the ring.
The rotor as shown in FIG. 16 of EP 1548171 includes cooling fins 42 and a radial embossing 43 at a predetermined position between adjacent fins. The fins are cut and bent from predetermined positions of a horizontal surface of the rotor frame for blowing air during rotation of the rotor 40, to cool and dehumidify the motor. Each embossing reinforces the rotor frame 41. The embossings 43 can be formed by a pressing operation.